1. Field of the Invention
The invention relates generally to valves for regulating the flow of a fluid medium and particularly to improvements in diaphragm valves.
2. Discussion of Prior Art and the Invention
More specifically, the invention relates to a diaphragm regulating valve for regulation of the flow of a fluid medium, with a number of flat diaphragm elements in mutual contact and insertible into the flow channel mounted between two housing halves and actuatable by at least one catch ring also mounted in the housing.
Diaphragm regulating valves afford substantial advantages over traditional shutoff devices such as slide valves, cocks, lifting valves, throttle valves, and so forth. The continuously variable aperture cross-section of the diaphragm regulating valve is always positioned coaxial with the axis of the pipe, so that the flow in the valve is not deflected and experiences only slight losses of pressure. The medium need not change direction repeatedly, as is the case with lifting valves.
The rate of flow can be determined with precision in every closing position, the flow characteristic in theory exhibiting the shape of a parabola. The accuracy of the characteristic is affected chiefly by the rate of leakage between the segments of the diaphragm and by the nature of the medium which is to be regulated. The actual shape of the characteristic approaches the theoretical parabolic form in the case of semifluid media where the rate of leakage is correspondingly lower.
A diaphragm regulating slide valve is known from Swiss Pat. No. 369,943, one whose diaphragm elements can be introduced into a flow channel perpendicular to the wall of this channel. There are between the individual elements relatively large gaps which cannot be sealed off even in the closed position. The state-of-the-art slide valve thus exhibits a high leakage rate, so that it is not suited for precise flow regulation and thus cannot be employed in place of a conventional regulating valve.
The state-of-the-art regulating slide valve has a movable regulating ring sealed off toward the exterior and on the two plane surfaces. Lateral sealing is effected against the housing or against the movable diaphragm elements. When the pressure inside the system rises, the pressure per unit area on the seals also increases, thus resulting in an increase in the displacement force. Consequently, structural limits are imposed on the state-of-the-art slide valves from the viewpoint of rated pressure.
As a result, the slide valve is massive and material-intensive in point of design, thus rendering manufacture a costly process. Installation of the slide valve is also complicated and expensive. Because of the high rate of leakage, it is suited only for semifluid media such as sludge, paste, concrete, etc. It cannot be employed for highly fluid media, let alone gaseous ones, and thus affords no decisive advantages over the conventional regulating valves.
The object of the invention is to create a diaphragm regulating valve in which the disadvantages of the state-of-the-art regulating slide valve are avoided. It is claimed for the invention that this is achieved in such a way that at least one of the housing halves is provided with supporting ribs forming a star for the diaphragm elements, said ribs projecting into the flow channel, and so that the ribs fully cover the contact edges of the diaphragm elements when the valve is closed. It is expedient for the contact edges of adjacent diaphragm elements to be graduated to a reciprocally equal extent.